The herpes viruses include the herpes simplex viruses (HSV), comprising two closely related variants designated types 1 (HSV-1) and 2 (HSV-2). These types are related immunologically, but most of their proteins carry distinguishing characteristics which allow them to be differentiated (See Morse et al., J Virol., 26(2), 389-410, 1978). The herpes simplex virus is a double stranded DNA virus having a genome of about 150 to 160 Kb, packaged within an icosahedral nucleocapsid, enveloped in a membrane. The membrane includes a number of virus-specific glycoproteins, the most abundant of which are gB, gC, gD, and gE. The proteins gB and gD are cross-reactive between IISV-1 and HSV-2.
HSV-1 and HSV-2 are responsible for a variety of human diseases, such as skin infection, oral and genital herpes, viral encephalitis, and the like. Infections in humans are characterized by episodes of epithelial eruptions involving active virus production alternating without clinical symptoms. The virus persists to cause recurrent disease and establishes both lytic and latent infections in the central nervous system (CNS) of its host, specifically the neural ganglia [See Stevens et al., J Exp. Med., 133:19 (1971)]. This tropism for the CNS may result in encephalitis [See Whitley, Virology, 2nd ed., Fields et. al., eds., Raven Press, N.Y. 1843-1887 (1990)]. Oral herpes (cold sores and fever blisters) is prevalent and is an inconvenience for approximately 60% of the population of industrial countries, whereas genital herpes is a major cause of sexually transmitted genital herpes which is in epidemic proportions in some populations. Infection with HSV can also cause more serious infections, the most serious of which are sight-threatening keratitis and life-threatening encephalitis. Also, herpesviruses have become increasingly important causes of human morbidity and mortality, especially in intensive care units for immunocompromised or immunosuppressed patients. Furthermore, HSV related disease in immunocompromised individuals such as newborns, leukemia patients, organ transplant recipients and AIDS patients has become an increasingly prevalent and difficult problem.
Several HSV vaccines have been prepared. S. Dundarov et al., Dev Biol Standard, 52:351-57 (1982) describes the treatment of humans with formalin-inactivated HSV in distilled water. GRB Skinner et al., Dev Biol Standard, 52:333-44 (1982) describes the treatment of humans with formalin-inactivated HSV in saline. L. Chan, Immunol, 49:343-52 (1983) describes the protective immunization of mice against HSV challenge by vaccination with gD in saline. Kino et al., U.S. Pat. No. 4,661,349 describes vaccines comprising purified HSV gB with alum. Person, U.S. Pat. No. 4,642,333 describes HSV gB and its administration to rabbits in Freund's adjuvant. L. R. Stanberry et al., J Infect Dis, 157:156-163 (1988) reports the use of rgD and rgB in a vaccine to ameliorate the symptoms of genital herpes infection in guinea pigs. Ho et al., reports the liposomal formulations of recombinant Herpes virus surface glycoprotein D-1 (HSV rgD-1) in the treatment and prevention of HSV disease (U.S. Pat. No. 5,149,529 incorporated herein by reference).
Presently, much of the antiviral research focuses on providing drugs with (i) improved oral bioavailability and pharmacokinetics which permit less frequent oral or topical dosing for suppressive treatment of herpes simplex virus (HSV) infections, (ii) different mechanisms of action for synergic effects in treating resistant HSV infections in the immunocompromised host and (iii) improved efficacy. Current strategies include developing antiviral agents that target enzymes or (viral factors essential for infection) or will inhibit other steps in the viral infection cycle, such as protein synthesis, capsid assembly or virus spread. In this regard, the viral DNA polymerase has been an important target for nucleoside analogs such as acyclovir, bromovinyl-deoxyuridine and Dihydroxy-phenylguanines (DHPG). However, lately, the severity of disease and the frequency of acyclovir resistance has increased in immunocompromised patients.
Currently, the in vitro and in vivo screens or methods used for identifying molecules that specifically impart HSV infection include a murine in vitro explant-cocultivation model [See Leib et al., J Virol. 63: 759 (1989)], a murine eye model [See Shimeld et al., J Gen. Virol. 71:397 (1990)], and other animal models (See U.S. Pat. No. 5,646,155, incorporated herein by reference). Some of these have limited specificity, and/or are time-consuming and/or are labor intensive. Thus, methods are needed for high throughput screening of anti-viral therapeutics against HSV infections, that provides rapid compound discovery in a cost efficient manner.